Department of Neurology and the BNI-ASU Center for Preclinical Imaging, Barrow Neurological Institute, St, Joseph's Hospital and Medical Center, 350 West Thomas Road, Phoenix, Arizona 85013, USA.
J Neuroinflammation. 2014 Feb 3;11:26. doi: 10.1186/1742-2094-11-26.
Chemokine (C-X3-C motif) ligand 1 (CX3CL1)/ CX3C chemokine receptor 1 (CX3CR1) signaling is important in modulating the communication between neurons and resident microglia/migrated macrophages in the central nervous system (CNS). Although CX3CR1 deficiency is associated with an improved outcome following ischemic brain injury, the mechanism of this observation is largely unknown. The aim of this study was to investigate how CX3CR1 deficiency influences microglia/macrophage functions in the context of its protection following brain ischemia.
Wild-type (WT) and CX3CR1-deficient (CX3CR1⁻/⁻) mice were subjected to transient middle cerebral artery occlusion (MCAO) and reperfusion. The ischemic brain damage was monitored by rodent high-field magnetic resonance imaging. Neurological deficit was assessed daily. Neuronal apoptotic death and reactive oxygen species (ROS) production were analyzed by immunostaining and live imaging. Activation/inflammatory response of microglia/macrophage were assessed using immunohistochemistry, flow cytometry, 5-bromo-2-deoxyuridine labeling, cytokine ELISA, and real-time PCR.
CX3CR1⁻/⁻ mice displayed significantly smaller infarcts and less severe neurological deficits compared to WT controls, following MCAO. In addition, CX3CR1⁻/⁻ MCAO mice displayed fewer apoptotic neurons and reduced ROS levels. Impaired CX3CR1 signaling abrogated the recruitment of monocyte-derived macrophages from the periphery, suppressed the proliferation of CNS microglia and infiltrated macrophage, facilitated the alternative activation (M2 state) of microglia/macrophages, and attenuated their ability to synthesize and release inflammatory cytokines.
Our results suggest that inhibition of CX3CR1 signaling could function as a therapeutic modality in ischemic brain injury, by reducing recruitment of peripheral macrophages and expansion/activation of CNS microglia and macrophages, resulting in protection of neurological function.
趋化因子（C-X3-C 基序）配体 1（CX3CL1）/CX3C 趋化因子受体 1（CX3CR1）信号在调节中枢神经系统（CNS）中神经元与驻留小胶质细胞/迁移巨噬细胞之间的通讯方面起着重要作用。尽管 CX3CR1 缺乏与缺血性脑损伤后的改善结果相关，但这一观察结果的机制在很大程度上尚不清楚。本研究旨在探讨 CX3CR1 缺乏如何影响小胶质细胞/巨噬细胞在脑缺血后的保护作用中的功能。
野生型（WT）和 CX3CR1 缺陷型（CX3CR1⁻/⁻）小鼠接受短暂性大脑中动脉闭塞（MCAO）和再灌注。通过啮齿动物高场磁共振成像监测缺血性脑损伤。每天评估神经功能缺损。通过免疫染色和实时成像分析神经元凋亡死亡和活性氧（ROS）产生。通过免疫组织化学、流式细胞术、5-溴-2-脱氧尿苷标记、细胞因子 ELISA 和实时 PCR 评估小胶质细胞/巨噬细胞的激活/炎症反应。
与 WT 对照相比，CX3CR1⁻/⁻ 小鼠在 MCAO 后表现出明显较小的梗死灶和较轻的神经功能缺损。此外，CX3CR1⁻/⁻MCAO 小鼠显示出较少的凋亡神经元和降低的 ROS 水平。受损的 CX3CR1 信号转导阻止了单核细胞来源的巨噬细胞从外周募集，抑制了中枢神经系统小胶质细胞和浸润性巨噬细胞的增殖，促进了小胶质细胞/巨噬细胞的替代激活（M2 状态），并减弱了它们合成和释放炎症细胞因子的能力。
我们的结果表明，抑制 CX3CR1 信号转导可作为缺血性脑损伤的治疗方式，减少外周巨噬细胞的募集和中枢神经系统小胶质细胞和巨噬细胞的扩张/激活，从而保护神经功能。
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